A variety of devices and methods have been developed to deliver a therapeutic or cosmetic agent to surfaces in the oral cavity. In particular, many systems which deliver a whitening agent to the teeth are available.
A person desiring whiter teeth can choose from professional whitening systems, or can purchase an over-the-counter tooth whitening device for use in the home. In the professional teeth bleaching market, dentists have traditionally used devices for delivery of home bleaching agents which are rigid and custom-fitted to an individual patient's dental arches. One type of delivery device is molded to closely fit a patient's dental arches. Another type of device is an “oversized” rigid custom dental appliance, which is formed by augmenting the facial surfaces of the teeth on stone models made from the patients' teeth, for example with linings such as die spacers or light-cured acrylics. A third type of device is a rigid, bilaminated custom-made dental appliance fabricated from materials ranging from soft porous foams to rigid, non-porous films. The non-porous, rigid thermoplastic shells of such bilaminated dental appliances may encase and support an internal layer of soft, porous foam which absorbs the bleaching agent.
After the custom appliance is fabricated, the dentist typically delivers the first bleaching treatment in the office, and instructs the patient on the proper procedure to dispense bleaching agent in the custom appliance at home. A sufficient amount of bleaching gel is provided so that the patient can perform the prescribed home bleaching regimen. The patient subsequently applies the bleaching agent daily (or as otherwise instructed) by dispensing the bleaching agent into the rigid custom dental appliance and placing the appliance over the dental arch for a specified period of time. At the end of a given treatment period, the dental appliance is removed, thoroughly cleaned to remove any remaining bleaching agent, and stored until the next application. The professional tooth whitening systems generally use a higher concentration of bleaching agent, and consequently the overall treatment period is shorter than that recommended for over-the-counter systems.
However, the rigid, custom-fabricated dental appliances used in professional tooth whitening systems require time-consuming and expensive office visits, laboratory tests and the fitting of each patient's dentition. Furthermore, any changes in the surface of the patient's teeth (such as fillings, crowns, and other accidental or therapeutic alterations of the dentition) affect the fit of the rigid custom dental appliance, and may warrant repeating the entire fabrication procedure. Refabrication of the appliance may also be required in the event of subsequent rebleaching treatments.
Moreover, patients who are inexperienced and unaware of the importance of precision often dispense an improper amount of bleaching agent into the appliance. Dispensing too little bleaching agent into the device results in a less efficacious treatment regimen. Dispensing an excessive amount of bleaching agent into the appliance can cause the agent to be displaced from the appliance into the oral cavity when the device is placed on the teeth, where the agent can be ingested. In addition to such displacement, the bleaching agent can spill or leak from these appliances into the oral cavity, and can cause an unpleasant taste sensation. Ingestion of the bleaching agent may also cause gingival irritation, burning, edema, nausea or allergic reactions. The risk of these more serious side effects increases with the number of treatments, and becomes most significant after the multiple treatments typically required to attain acceptable clinical results. Patients who self-administer bleaching or other medicinal agents may also fail to provide the careful maintenance, cleaning, and storage necessary to ensure that the rigid custom dental appliance performs adequately throughout its entire service life.
There are additional drawbacks with custom bilaminated dental appliances, including occlusion and retention of bleaching agent. Furthermore, cleaning and maintenance of foam-lined dental appliances may be problematic, due to the high surface area and pore volume of the foam materials typically used in such appliances.
Oversized rigid custom dental appliances also have additional drawbacks, including occlusions in the augmented region, increased appliance fabrication time and cost, irritation from the lip of the appliance contacting the gingival region, and decreased retention of the bleaching agent within the target area.
In order to avoid the high cost and inconvenience of professional tooth whitening systems, one may purchase non-professional, “over-the-counter” tooth whitening systems. Some versions of the over-the-counter systems contain a generic “one size fits all” appliance and a container of bleaching gel to be dispensed into the appliance, for example as described in U.S. Pat. No. 3,416,527 of Greenberg and U.S. Pat. No. 3,527,219 of Hoef. However, such generic appliances often have a greater void between the interior walls of the appliance and the teeth as compared to most professionally fitted appliances. Hence, in order to insure intimate contact of the bleaching agent and the teeth surfaces, more bleaching agent is required. Furthermore, the poorer fit of the generic device means a greater loss of bleaching gel into the oral cavity, with the attendant problems described above for the professional tooth whitening appliances. Thus, the leakage problems of professional tooth whitening systems are exacerbated by over-the-counter systems in which the user dispenses the whitening agent into the device. The generic over-the-counter devices also tend to be bulky and uncomfortable in the mouth.
Over-the-counter systems with pre-dispensed bleaching agent are also available. The bleaching agents used in such over-the-counter systems are either viscous liquids or gels containing peroxide compounds. The peroxide compounds are typically provided in hydrated (i.e., active) form, or the peroxide compounds become hydrated due to moisture in the agent or the surrounding air. A typical bleaching agent is a carbamide peroxide gel, in which hydrogen peroxide is coupled to urea in either an anhydrous glycerin base or a soluble, aqueous carboxylic acid polymer base. Upon hydration, the carbamide peroxide breaks down into urea and active peroxide. The active peroxide subsequently breaks down into water and oxygen. Over time, the inherent instability of hydrated peroxide bleaching agents reduces the efficacy of tooth whitening systems with pre-dispensed bleaching agents. The shelf-life of such systems is therefore limited.
U.S. Pat. No. 5,310,563 of Curtis et al. discloses an over-the-counter tooth whitening device in which a putty-like material encapsulating the bleaching agent is molded around the teeth. The putty is held in place by mechanical engagement with undercut surfaces of the teeth, and by friction. The bleaching agent migrates from the composition to the gums and tooth surfaces, rather than being directly in contact with them, which significantly increases the required wearing time. The putty also tends to slip off the teeth, further reducing the efficacy of this type of system.
U.S. Pat. Nos. 5,575,654 and 5,863,202 of Fontenot disclose an over-the-counter tooth whitening system containing prepackaged moldable dental appliance that can be adapted to fit the dental arch, which contains a premeasured amount of medicinal or bleaching agent. It has been observed that the Fontenot device frequently has the problems of bulk and compromised fit. The pressure required to mold the device to the dental arch can also force the bleaching agent out of the device and into the oral cavity.
U.S. Pat. No. 5,980,249 of Fontenot describes a whitening system consisting of a prefabricated, U-shaped dental appliance of hydrophilic foam. The bleaching agent is incorporated or invested in the foam. This device has drawbacks similar to those described above for professional tooth whitening systems using custom bilaminated dental devices. Such drawbacks include occlusion and retention of bleaching agent in the foam, and extrusion of the bleaching agent into the oral cavity upon application of the pressure required to form the device to the user's teeth.
U.S. Pat. Nos. 5,879,691, 5,891,453 and 5,894,017 of Sagel et al. describe over-the-counter tooth whitening systems consisting of flat, flexible strips coated on one surface with an adhesive gel containing a bleaching agent. The strips are meant to be folded over the teeth by the user, with the bleaching agent in contact with, and holding the device onto, the teeth. However, the strip does not adhere well to the tooth surface, and the device tends to slip off the teeth in use.
The bleaching gel is also poorly attached to the Sagel et al. flexible strip, and often adheres to the user's fingers during the manipulations required to fold the strip in place over the dental arch. The potential for contamination of the strip by the user's fingers during routine manipulation is high. Moreover, the bleaching gel can be transferred from the user's fingers to the clothes (which may then be stained or bleached), or to sensitive areas of the body like the eyes, which may cause extreme discomfort. The bleaching gel will also adhere to itself and delaminate from the flexible strip if the user inadvertently folds the strip in upon itself during placement onto the teeth. Such delamination of the bleaching gel reduces the efficacy of the whitening system. Upon removal of the Sagel et al. strip from the teeth, a quantity of the bleaching agent can also adhere to the teeth. This leftover bleaching agent leaves an unpleasant taste in the mouth, and is easily ingested.
Moreover, most of the bleaching gel content of the Sagel et al. strip is delivered and begins to degrade as soon as the strip is placed in the mouth, resulting in reduced efficacy of the whitening system. Repeated and prolonged use of the Sagel et al. strips is thus required to achieve the desired whitening effect.
Over-the-counter whitening systems similar to those described in the Sagel et al. patents are disclosed in U.S. Pat. Nos. 5,989,569 and 6,045,811 of Dirksing et al. The Dirksing et al. system consists of a deformable flat wax strip carrying the same type of bleaching gel as the Sagel et al. strips. Here again, the bleaching gel is poorly adhered to the wax strips, and the Dirksing et al. system likely suffers from the same problems of difficulty of use and reduced efficacy as described above for the Sagel et al. strips.
The known professional and over-the-counter tooth whitening systems can also be used to deliver other oral care agents, such as medicines or antibiotics, to the teeth and gingival tissue. However, the drawbacks described above for the tooth whitening systems are also present when the systems are used to deliver other oral care agents.
What is needed, therefore, is an over-the-counter device for delivering an oral care agent, for example a tooth whitening agent, in which a pre-measured amount of oral care agent is contained within a device that is firmly held onto a user's teeth, and which does not release the oral care agent into the oral cavity in appreciable quantities. The device should also be configured so that the user does not contact the oral care agent during routine manipulation of the device into place over the dental arch. The layer which delivers the oral care agent should also be sufficiently secured to the device so that no residue is left on the user's fingers if the layer inadvertently touched, and no residue is left on the teeth upon removal of the device. Furthermore, the oral care agent should be activated and released from the device over time, so that efficacy of the agent is maximized and the number and duration of each application is reduced.